Pressurized protective suits are used in hostile environments, such as, environments containing hazardous materials and in high altitude environments, including outer space. Pressurization of such suits causes them to become rigid so that the user's movements when wearing the suit can be severely restricted. Accordingly, such suits include a variety of joints so that the user can perform tasks while wearing the suit. These joints have included neck joints, shoulder joints, elbow joints, wrist joints, waist joints, hip and thigh joints, knee joints, and ankle joints.
To provide ease of movement, prior joints have included low friction bearings. In addition to low friction, these bearings have also had low leakage so as to maintain a separation between the internal environment of the suit and the external environment. MacKendrick et. al., U.S. Pat. No. 4,596,054, shows a construction of a prior art low friction, low leakage bearing which employs ball bearings held in integral metal races with the dynamic interface between the races being sealed by an elastomeric lip seal.
One of the critical criteria for a pressurized protective suit which is to be used in a "one g" environment is the overall weight of the suit. Overall weight is also important for suits which are to be used in outer space since the training of astronauts in such suits often takes place on earth. To date, weight minimization has involved the use of relatively light weight materials, such as, plastics, polymer reinforced fabrics, and the like, to form the body of the suit.
Because of their criticality, the bearings used in the joints of pressurized protective suits have continued to be made of relatively heavy metals. Prior to the present invention, light weight bearings composed substantially of non-metallic materials have not been available to the art. In the early days of the space program, bearings made of aluminum were used, however, those bearing were found to wear rapidly and, as a result, are no longer used. Instead, stainless steel bearings are used which are both heavier and more expensive than bearings made of aluminum. The challenge to the art has been to produce bearings which have low torque, high reliability, and long life cycle properties which are comparable to bearings made from high density metals and which, at the same time, have a significantly reduced weight in comparison to such heavy bearings.
In addition to the foregoing properties, the desired light weight bearings need to have pressure retaining characteristics sufficient to withstand the internal pressures used in pressurized protective suits, i.e., the bearings must exhibit very low leak at the operating pressure of the suit. In general terms, the higher the pressure the bearing can withstand without developing significant (higher) torque, the better.
Bearings employing race wires have been commercially produced. See, for example, Wireglide Bearings, Inc.'s product brochure entitled "USB-Ultra Slim Bearings, Wire Race Bearings, Wire Elements, Retrofit Services", 1985; JC Engineering International Ltd.'s product brochure entitled "Ultra Slim Bearings", 1984; and Rotek Incorporated's product brochure entitled "Large-Diameter Ball and Roller Bearings" 1973, page 7. These bearings, however, have not had low leak characteristics and have not been used in constructing the joints of pressurized protective suits.